This disclosure relates to a motor cooling system for a motor-driven compressor in an aircraft On Board Inert Gas Generating System (OBIGGS).
Aircraft and other vehicles may include an OBIGGS for generating inert gas. An OBIGGS generally includes an air separation module (ASM), which separates air into an inert nitrogen-enriched air (NEA) stream and a permeate oxygen enriched air (OEA) stream. The NEA stream may, for example, be used at the fuel tanks of an aircraft or vehicle.
OBIGGS designs may include a heat exchanger and a motor-driven compressor (MDC) system. The MDC system may include first and second compressors. The heat exchanger may be arranged in a ram-type air duct. During ground operation, cooling airflow over the heat exchanger is usually provided by an ejector downstream of the MDC system, which creates a low pressure area and draws air across the heat exchanger. The ejector air is generated from MDC second compressor outlet. During various flight and day temperatures (i.e., cold to hot day) conditions, the airflow over the heat exchanger may vary. For example, in the hot day condition there may not be enough airflow during ground operations to sufficiently cool the heat exchanger.
Additionally, the MDC is usually cooled by a cooling loop which may pass through an intercooler. Presently, the MDC cooling loop draws air from the outlet of the first compressor, and the air is ultimately discarded overboard after passing through the cooling loop. This lowers the efficiency of the MDC cooling loop during ground operations.
The ASM receives compressed air from the MDC. However, current MDC cooling designs do not effectively provide adequate ASM inlet temperature during cruising. Furthermore, the ejector can lower the flow rate of air available in the MDC system, which in turn decreases the amount of air available for the ASM.